Hyperglycemia is the major cause of diabetic microvascular complications including retinopathy, nephropathy and neuropathy. Early diagnosis of microvascular complications in these tissues has been difficult due to the long duration of disease required for the onset of clinical symptoms and the general inaccessibility of vascular and neurological tissues for analysis. Animal studies have clearly demonstrated that microvascular pathologies in the retina and renal glomeruli can manifest years before the onset of clinical symptoms. Activation of protein kinase C (PKC), specifically the B isoforms and increases in VEGF levels in the retina and renal glomeruli have been shown to correlate with severity of hyperglycemia induced vascular pathologies in diabetic animals. However, due to tissue access problems, almost all of the data regarding the increases in PKC activities and VEGF levels have been measured in vascular tissues from animal models of diabetes. Plasma levels of PKC do not exist and plasma VEGF levels do not consistently correlate with corresponding levels in the microvascular tissues. Recently, we have measured PKC activities in the circulating mononuclear cells and they correlated with the severity of diabetic retinopathy and nephropathy in type 1 and 2 diabetic patients. In addition, the expression of VEGF levels in the circulating monocytes from humans and diabetic rats can be increased by PKC activation. Similarly, increases in PKC activation and, potentially, VEGF expression in the circulating monocytes responded in parallel to diabetes in the vascular tissues of retina, renal glomeruli and arteries. In addition, monocyte activation has been noted by multiple studies in the cardiovascular and microvascular circulations including the retina and renal glomeruli from diabetic animals. Thus, we are proposing to test the hypothesis that increases in PKC activation and VEGF levels in the circulating monocyte are similar to those found in the retina and renal glomeruli in response to hyperglycemia or diabetes. Therefore, the ability to measure VEGF levels and PKC activities in circulating monocytes, which can be easily accessed, could be used as surrogate markers of diabetic microvascular disease especially diabetic retinopathy and nephropathy. We are proposing to test three specific aims in diabetic and control patients 1) To correlate VEGF levels with PKC activity in circulating monocyte with severity of retinopathy and nephropathy. 2) To determine whether glycemic control can alter the activation of PKC and VEGF levels in circulating monocytes. 3) To correlate PKC activity and VEGF levels in circulating monocytes with VEGF level in the ocular fluids obtained during surgery. These data can provide definitive evidence to determine whether further studies are needed to establish these two parameters in the circulating monocyte as surrogate markers of diabetic microvascular diseases.